Patent GB-392078-A (GB)
Title: Improvements in multiple position rotary or oscillatory electric switches
IPC: H01H19/64
Filed: 1932-10-28
Abstract: 392,078. Retractive switches. ENGLISH ELECTRIC CO., Ltd., 28, Kingsway, London, and HEATH, A. A., Lydstep, Rowley Park, Stafford. Oct. 28, 1932, No. 30304. [Class 38 (v).] Contacts ; cam actuation.-Switch contacts or operating members, e.g. cams, are mounted side by side in any one of a large number of relative angular positions by fitting them over regular polygonal bushes e which in turn fit over a regular polygonal or like-shaped shaft d having a different number of sides from the exterior of the bushes. In applying the invention to a multiple contact switch for closing or tripping a circuit-breaker, five switch units are mounted on a hexagonal shaft d which can be moved on either side of a central position by means of a handle n. The first four units are directly driven by the shaft, and comprise contact members f mounted on the pentagonal surfaces of bushes e or l, which are formed with a hexagonal bore to fit the shaft. The first. and fourth contact members are held between flanges on the bushes e and insulating cover sleeves g formed with pentagonal bores to fit the bushes, while the second and third are connected together by a conducting sleeve k. The fifth switch unit, shown on the right in Fig. 3, is free to rotate on the cylindrical outer surface of a bush p having a hexagonal bore to fit the shaft. This unit is provided at one end with a disc r, with notches adapted to engage a spring-pressed ball s to hold the unit in one of two positions, and at the other end with a disc t provided with an arcuate recess t<1> adapted to be engaged by a driving pin u<1> on a crank u secured to the shaft d. All the contact members f may be made by cutting away parts of the rims of cup-shaped washers of thin metal. The fixed contacts h<2> may be resiliently mounted on rigid brackets h<1> by means of flexible strips h<3>, pins h<4> and compression springs h<5>, as shown in Fig. 6. Correct sequence of operations may be ensured by the co-operation of a spring blade or pawl A, carried by the shaft d, with a fixed plate B having a ratchet tooth B<3>, as described in Specification 392,135. A self-centring device, for returning the switch to the mid-position after actuation in either direction, comprises a lever E secured to the shaft d, an equalizing bracket D pivotally mounted on the shaft, and a bridge-piece F urged towards fixed pins a<2> by springs H coiled about pins G, which are pivoted to the bridgepiece and pass through holes D<1> in the bracket D. When the shaft d is rotated from the central position, one of a pair of pins E<1> on the lever E engages the bridge-piece and causes the latter to turn about one of the pins a<2> as a fulcrum, thereby compressing the springs H, the pressure applied to one spring being transmitted to the other through the equalizing bracket. On releasing the handle, the springs return the shaft d to the central position. In operating the switch to close a circuit-breaker, the shaft d is rotated in a counterclockwise direction, as viewed in Fig. 5. The contact member of the fourth unit momentarily closes a preparatory circuit, which is not completed when the shaft is rotated in the reverse direction to trip the circuit-breaker. When the shaft has rotated through 90‹ the contacts of the first three units complete a circuit for closing the circuit-breaker, while the loose contact of the fifth unit is driven by the lever u and prepares a circuit for an indicator. On being released, the switch is returned to the off position by the self-centring device, the loose contact unit being held in the contact-making position by the ball catch s. The engagement of the pawl A with the tooth B<3> now prevents the switch from being again moved to the position for closing the circuit-breaker until it has been first moved in the reverse direction to the " tripping " position. If the circuit-breaker is tripped automatically it completes the indicator circuit which has already been prepared by the loose contact unit.